Ultrasonic precipitation of manganese carbonate: Reactor design and scale-up

This study discusses the reactor design and a possible scale-up strategy for ultrasonic precipitation of manganese carbonate. Preliminary experiments, performed in a 200 mL continuously stirred tank reactor (CSTR) equipped with an ultrasonic transducer or probe, identified the importance of generating a homogenously distributed ultrasonic field of about 40 kHz to improve the sphericity of the powder. In this lab-scale reactor, spherical particles with a tap density of more than 2.0 g/cm3 were obtained under sonication, compared to only 1.3 g/cm3 during silent conditions. Alternatively, a design with an ultrasonic unit in a recirculation loop resulted in a similar relative improvement compared to silent conditions. However, since the recirculation reactor did not reach a tap density of above 2.0 g/cm3, the scale-up of this configuration was discarded. In the end, a basic CSTR was scaled to 50 L by using a single radial oscillating probe, operating at 40 kHz and 1 kW. This semi-pilot scale reactor was able to produce particles with a tap density of about 90% of the value attained at lab-scale although the power density was reduced by more than half.